Software programs are error prone and, therefore, should be validated for correctness. Simulation is an often-used technique for debugging code. But simulation typically leaves large portions of code untested, thereby greatly increasing the chance that bugs remain in the program. To alleviate this problem, various metric methodologies have been proposed that give a percentage of the amount of the description that is exercised by the simulation test vectors. Most of these software coverage metrics consider excitation, but fail to address observation.